Corona free coupling assembly for coaxial cables

ABSTRACT

A corona free coupling assembly for high voltage coaxial cable comprising an elastomeric body of insulating material having an elongated bore for receiving end portions of the cables, tubular inner shield means embedded in the body in coaxial alignment with the bore and spaced from opposite ends thereof; a tubular connector sleeve is inserted into the bore within said inner shield means for connecting the central conductors in end-to-end relation; conductive spring means is mounted on the connector sleeve including a deflectable free end portion normally biased outwardly for contact against the inner shield means embedded in the elastomeric body. The spring means is deflectable inwardly against the sleeve while being inserted into the elastomeric body with the connected cables. An outer conductive shield means is provided around the insulated elastomeric body for connecting the outer shielding systems of the cables.

United States Patent [72] Inventor Donald 0. Misare Riverside, ill. 1211 Appl. No. 868,548 [22] Filed Oct. 22, 1969 [45] Patented May 25, 1971 [73] Assignee Joslyn Mfg. and Supply Co.

- Chicago, Ill.

[54] CORONA FREE COUPLING ASSEMBLY FOR COAXIAL CABLES 4 Claims, 6 Drawing Figs.

s2 u.s. Cl rm/73, 174/88 [51] Int. Cl "02g 15/08 [50] Field oiSearch 174/73, 73.1, 88, 88.2; 339/143 (C) [56] References Cited UNlTED STATES PATENTS 1,779,415 10/1930 Austin l74/73(.l) 3,290,428 12/1966 Yonkers 174/73 3,453,372 7/1969 Gahiretal. 3,485,935 12/1969. Kreuger Primary Examiner-Laramie E. Askin Attorney-Mason, Kolehmainen, Rathburn and Wyss 174/88X l74/73X ABSTRACT: A corona free coupling assembly for high voltage coaxial cable comprising an elastomeric body of insulating material having an elongated bore for receiving end portions of the cables, tubular inner shield means embedded in the body in coaxial alignment with the bore and spaced from opposite ends thereof; a tubular connector sleeve is inserted into the bore within said inner shield means for connecting the pm d a 25, 1971 2 Sheets-Sheet 2 UQN w ON IN VliN'I'nR: DONALD O. MISARE BY:

CORONA FREE COUPLING ASSEMBLY FOR COAXIAL CABLES The present invention relates to a new and improved, corona free coupling assembly for connecting or splicing together high voltage coaxial cable of the type commonly used in underground power distribution systems. The present invention is an improvement over the cable connector shown in FIG. 8-of US. Pat. No. 3,290,428 and is especially designed to eliminate corona discharge which is often present in prior art coupling and terminal assemblies used with high voltage coaxial cables and the like.

Corona problems develop whenever a sufficient electrical voltage is present between spaced conductors separated by air spacing or air pockets. Corona, in addition to wasting power, is deleterious to many insulating materials and often causes deterioration and weathering thereof. In addition, corona envelopes cause radio interference and noise, which are objectionable.

The present invention has for an object the provision of a corona free coupling assembly for use in connecting high voltage coaxial cables of the type used in high voltage underground power distribution systems.

Another object of the present invention is to provide a new and improved corona free coupling assembly which is low in cost, easy to assemble and install, and reliable in operation.

Another object of the present invention is to provide a new and improved corona free coupling assembly for use with high voltage coaxial cables wherein the voltage stress gradient in insulating material of the coupling assembly is uniform and symmetrical about the cable and wherein no electrical stress is applied across air-spaced conductors.

Another object of the present invention is to provide a new and improved corona free coupling assembly of the character described having new and improved means for locking the coupling together to prevent inadvertent withdrawal of one of the connectors from the coupling assembly.

Briefly, the foregoing and other objects and advantages of the present invention are accomplished in an illustrated embodiment comprising a new and improved coupling assembly for splicing or connecting together high voltage coaxial cables. The assembly includes a body of ela's tomeric insulating material having an elongated axial bore'bpen at opposite ends for receiving the terminal end portions-ibf the cables. Tubular inner shield means is embedded in the body in'coaxial alignment with the bore and is spaced from opposite ends of the bore. A tubular connector sleeve is insertedinto the bore and inside the inner shield means to connect the central conductors of the coaxial cables in end-to-end relation. A conductive spring means is mounted on a conducting sleeve and includes a deflectable free end portion which is normally biased outwardly thereof for making electrical contact with the inner shield means, once inserted into position centered within the elastomeric body. The free end of the spring means is deflectable against the sleeve during insertion of the sleeve into the centered position in the elastomeric body. An outer conductive shield means is provided around the elastomeric insulating body for connecting the outer shielding system of the connected cables so that a uniform and symmetrical voltage gradient or stressis established between the inner and outer shield system after the cables are'connected in the coupling assembly.

For a better understanding of the present invention, reference should be had to the following detailed description taken in conjunction with the drawings, in which:

FIG. 1 is a side elevational view of a coupling assembly constructed in accordance with the features of the present invention and shown with the end portion of one coaxial cable fully inserted and ready for attachment with the connector sleeve of the apparatus;

FIG. 2 is an elevational view of the coupling assembly shown in a partially assembled condition with the connector sleeve installed and interconnecting the central conductors of the coaxial cables;

the coupling assembly after the sleeve connected coaxial cables have been centrally positioned longitudinally of the coupling assembly with the connecting sleeve spaced between opposite ends of the embedded inner shield means in the elastomeric filler of the coupling assembly;

FIG. 4 is an elongated longitudinal sectional view illustrating the coupling assembly after assembly has been completed but before the spring has been released to compress the elastomeric body;

FIG. 5 is a transverse cross-sectional view taken substantially along lines 5-5 of FIG. 4; and 7 FIG. 6 is a perspective view of the connecting sleeve and conductive spring means of the coupling assembly.

Referring now, more particularly, to the drawings, therein is illustrated a new and improved, corona free, coupling assembly 10 especially adapted for connecting or splicing together the ends of a pair of high voltage, coaxial cables 12 and 14. The cable 12 includes a central conductor 12a surrounded by a concentric insulating jacket 12b, preferably formed of molded polyethylene material, and the jacket 12!: is in turn surrounded by a conductive outer shielding system 12c, which may comprise a wrapping of conductive tape, or the like. Similarly, the coaxial cable 14 includes a central conductor 14a surrounded by an insulating jacket 14b which in turn is covered by an outer shielding system 140. A plurality of spirally wound neutral wires 12d and 14d (FIG. 4) are wound over the respective outer shields 12c and 140 of the cables.

Inaccordance with the present invention, the coupling assembly 10 includes an elongated body or filler 16 formed of elastomeric insulating material and provided with an elongated axial bore having opposite end portions 16a with a diameter substantially the same as the nominal diameter of the insulating covers or jackets 12b and 14b of the coaxial cables. lnterrnediate the end portions 16a of the bore, the elastomeric body 16 is formed with an enlarged central bore portion 16b,

. having a diameter greater than the bore sections 16a in order to accommodate a tubular, conductive, inner shield 18, which is embedded in the central portion of the elastomeric filler body. A pair of annular rings 20, formed of insulating material, are mounted at opposite ends of the inner shield tube 18, and the rings, preferably .fonned of strong, rigid material, serve as end stop surfaces and define opposite end walls of an annual central chamber 22.

Opposite ends of the filler body 16 are shaped with frustoconically tapered end portions 16c in order to provide a symmetrical increase in insulation strength adjacent the regions where the outer shield systems 12c and 14c are discontinued. A pair of frustoconically shaped, cuplike, conductive outer shielding members 24, formed of metal or the like, are mounted on theend portions of the elastomeric body to protect and shield the same and to continue the outer shield system from the cables around the main body of the'fitting. Between the frustoconical end portions 16c, the filler body 16 is encased within a hollow, metallic cylindrical outer shield member 26 formed with a relatively small, radially inwardly directed end flange 260 at the right-hand end (as viewed in FIGS. 2 through 4). The flange 26a bears against a radial flange 24a formed on the larger end of the right-hand cuplike outer shield member 24. At the left-hand end, a washerlike end wall 28 is welded or otherwise secured to the outer shield tube 26, and the end -wall has a central aperture 280 slightly larger in diameter than the maximum diameter of the cables 12 or 14 which will be used with the coupling assembly 10.

Between the end wall 28 and a radial flange 240 at' the larger end of the left-hand, cuplike, outer shield member 24, a coiled compression spring 30 is mounted, and after the coupling. is fully assembled, the spring is released froma prestressed. or compressed condition (as shown irf'FlG. 4). When the spring is released, the left-hand, cuplike, outer shield member 24 is forced towards the right and exerts compression on the elastomeric filler body 16 to expel all of the air from between the outersurfaces of .the filler body 16 and the outer shield members 24 and 26. Compression on the end of the tiller body by the spring also expels airflow from between the interfacing surfaces of the cables and the bore surfaces of the filler body.

' During initial insertion of the cables 12 and 14 into the bore of the filler body 16, the compression spring 30 is maintained in a compressed condition, as shown, and exerts no force on the elastomeric filler body, thereby permitting easy insertion and sliding of the cables and a sleeve 38 along the axial bore into the filler body. During this period, the compression of the spring 30 is maintained by an annular ring 32 disposed between the right-hand end coil of the spring and the end flange 24a of the left-hand outer shield cup 24. The retaining ring 32 is provided with a pair of legs 34 extending longitudinally of the coupling assembly which project outwardly through slots formed in the end wall 28. Each leg 34 has an aperture adjacent the outer end thereof for receiving the shank of a removable key pin 36 having a looped end 3611 which can be easily grasped for pulling or removing the pins, as shown by the arrows A.

,When the key pins are released by outwardpull, the spring 30 is released to expand from the compressed condition shown and moves the left-hand shield cup 24 into compression against the left-hand end portion 16c of the elastomeric filler body 16. As this occurs, any air entrapped between the cables 12 and 14 and the bore of the filler body is expelled toward the central chamber 22 or out the opposite end of the filler body.

As a first step, preliminary to making a connection or splice between the ends of the cables 12 and 14, each cable is especially prepared by stripping back the neutral wires 12d and 14d for a prescribed distance from the cable end and then stripping back a shorter length of the outer shield tapes 12c and 14c. The neutral wires 12d and 14d are braided or twisted into cablelike conductors (FIG. from the point of strip back on the cable body and at least one neutral wire of each group is wound around the cable body in several adjacent radial rings, .as at 12c and 142 (FIG. 4) to positively secure the neutral conductors to the cable body so that further unraveling of the neutral wires does not occur. A selected shorter length of the insulating bodies 12b and 14b is stripped back and removed, leaving shortlengths of the central conductors 12a and 14a exposed and ready for splicing, as shown in FIG. 1. The prepared cable 12 is then fully inserted through the hollow bore of the filler body 16 from left to right (arrow B," FIG. 1) until the exposed end portion of the central conductor 12a is fully'outward of the right-hand conical shielding cup 24.

A compression-type tubular connector sleeve 38, having an elongated bore 38a substantially the same or slightly larger in diameter than the nominal diameter of the central conductors 12a and 14a is inserted onto the exposed end portion of the central conductor 12a (arrow C," FIG. 1), and the exposed central conductor 14a of the cable 14 is then inserted into the right-hand end of the connector sleeve 38, as indicated by the arrow D" in FIG. 2. The connector sleeve 38 is then compressed radially inwardly with a crimping tool, or the like. The crimping actioncompresses the sleeve radially inwardly and positively connects together both mechanically and electrically the exposed portions of the central conductors 12a and 14a.

The tubular connector sleeve is slightly longer than the combined length of the exposed end portions of the central conductors 12a and 14a in order to provide a slight space 38 b (FIG. 2) between opposite end faces bf the central conductors when the prepared cables 12 and 14 are fully inserted into the sleeve 38 with the ends of the insulating covers 12b and 14b abutting'opposite ends of the sleeve A conductive contact spring 40 is pivotally mounted on the compression sleeve 38 and the spring includes a shorter leg or pivot axle portion 40a which extends transversely through aligned openings in the sleeve walls adjacent the center thereof. The spring includes an elongated, free end portion or contact leg 40!: at one end of the pivot leg 40a, and in order to permanently retain the spring on the connector 38, a short retainer leg 400 is provided at the opposite end of the pivot leg 40a. The free end portion of the contact leg 40!) is normally extended outwardly of the sleeve 38 at a substantial angle relative to the longitudinal axis thereof, as shown in FIG. 2, and the leg 40b is pivotal about its inner end around the axis of the pivot leg 40a as represented by the arc in FIG. 6.

After the compression sleeve is secured in place, the connected cables 12 and 14 are moved from right to left, as indicated by the arrow B (FIG. 3) until the sleeve 38 is centered midway between opposite ends of the conducting tube 18 (FIGS. 3 and 8). In order to indicate when the sleeve 38 is in the centered longitudinal position in the filler body, a marker tape 42 is provided on the cable 14 at the prescribed distance from the cable and during the cable preparation.

As the sleeve 38 and spring 40 pass through the right-hand bore'section 16a of the filler body 16, the free end portion of the contact leg 40b is deflected inwardly against the body of the sleeve 38 by the pressure of the elastomeric filler. Once bles l2 and 14, sleeve 38, and spring 40 have moved from right to left through the bore of the filler body 16 far enough for the outer end of the contact spring leg 40b to clear the right-hand stop ring 20, engagement between the end of the leg 40b and the ring 20 prevents withdrawal of the cables from the filler body in a direction opposite to the arrow E"; however, if desired, the cables can be moved in the direction of the arrow E" from right to left. Outer surfaces of the cable end portions and sleeve 38 are greased to provide for easy sliding through the bore of the filler body 16, and the grease aids in expelling any entrapped air between the cables and the bore surface.

The spring 40 establishes electrical contact between the embedded inner shield tube 18 and the central conductors 12a and 14a of the spliced cables, and the air entrapped within the annular space 22 is not subjected to electrical stress. Accordingly, there is little chance of corona problems developing within the air space 22 because the inner shield tube 18 is maintained at thesame electrical potential as the sleeve 38 and central conductors 12a and 14a. The inner shield tube 18 is in symmetrical, coaxial relation within the outer shield cover 26 and conical end cups 24, and the elastic filler 16 is spaced between the inner and outer shield system to provide the necessary increased insulation strength.

The neutral conductors, comprising the outer shielding wired 12d and 14d of the respective cables, are braided into bundles and are connected externally of the housing 26 with a compression connector sleeve 44 (FIG. 5) similar to the sleeve 38. The neutral wires are grounded to and held against the housing 26 with tape wrappings 46, as needed, and one or more of the neutral wires is connected to a suitable grounding lug 28b (FIG. 4) on the end wall 28.

The coupling assembly 10 provides a corona free means for connecting or splicing together high voltage coaxial cables. The spring 30 maintains compression on theelastic filler body 16 to maintain air-free interfacial engagement between the cable insulation jackets 12b and 14b and the filler bore sections 16a, and permits expansion and contraction of the filler as temperature changes occur. The spring contact member 40 maintains electrical contact between the central conductors 12a and 14a, sleeve 38, and the inner shield tube 18, so that a concentric and symmetrical inner shield system obtains within the filler body. This arrangement prevents corona formation even though the chamber 22 may contain air.

What I claim as new and desire to be secured by Letters Patent of the United States is:

l. A corona free coupling structure comprising a pair of high voltage coaxial cables having outer shielding systems and a coupling assembly including a filler body of elastomeric insulating material having an elongated bore open at opposite ends receiving the end portions of said pair of cables; tubular, conductive inner shield means embedded insaid body in coaxtact between said sleeve and said inner shield means; conductive outer shield means around said insulating body connecting the outer shielding systems of said cables; said inner shield means having an internal diameter greater than the diameter of opposite end portions of said bore in said filler body extending outwardly in opposite directions from the opposite ends thereof, said inner shield means defining an annular space around said connector sleeve and cables within said body for accommodating the deflectable free end portion of said conductive contact means; and a pair of concentric, rigid, insulating spacer rings at opposite ends of said inner shield means, said rings having an inner diameter substantially equal to the diameter of said end portions of said bore and defining end walls of said annular chamber, one of said end walls being engageable by the free end of said conductive contact means to prevent withdrawal of said cables and conductor sleeve from said bodyin a longitudinal direction opposite the direction of insertion.

2. A corona free coupling structure comprising a pair of high voltage coaxial cables having outer shielding systems and a coupling assembly including a filler body of elastomeric insulating material having an elongated bore open at opposite ends receiving the end portions of said pair of cables; tubular, conductive inner shield means embedded in said body in coaxial alignment in said bore and spaced from said opposite ends thereof; a tubular connector sleeve inserted into said bore and said inner shield means connecting the central conductors of said cables in end-to-end relation; conductive contact means mounted on said conductor sleeve including a deflectable free and portion biased outwardly thereof making electrical contact between said sleeve and said inner shield means; and conductive outer shield means around said insulating body connecting the outer shielding systems of said cables; said conductive contact means includes a pivot leg extending transversely through said connector sleeve adjacent the central portion thereof for supporting the inner end of said free end portion for pivotal movement.

3. The coupling structure of claim 2 wherein said free end portion is pivotal between oppositely extending positions on a plane longitudinally of said connector sleeve.

4. The coupling structure of claim 3 wherein said free end portion is normally biased to extend angularly outwardly of said sleeve while on said longitudinal plane. 

1. A corona free coupling structure comprising a pair of high voltage coaxial cables having outer shielding systems and a coupling assembly including a filler body of elastomeric insulating material having an elongated bore open at opposite ends receiving the end portions of said pair of cables; tubular, conductive inner shield means embedded in said body in coaxial alignment in said bore and spaced from said opposite ends thereof; a tubular connector sleeve inserted into said bore and said inner shield means connecting the central conductors of said cables in end-to-end relation; conductive contact means mounted on said conductor sleeve including a deflectable free end portion biased outwardly thereof making electrical contact between said sleeve and said inner shield means; conductive outer shield means around said insulating body connecting the outer shielding systems of said cables; said inner shield means having an internal diameter greater than the diameter of opposite end portions of said bore in said filler body extending outwardly in opposite directions from the opposite ends thereof, said inner shield means defining an annular space around said connector sleeve and cables within said body for accommodating the deflectable free end portion of said conductive contact means; and a pair of concentric, rigid, insulating spacer rings at opposite endS of said inner shield means, said rings having an inner diameter substantially equal to the diameter of said end portions of said bore and defining end walls of said annular chamber, one of said end walls being engageable by the free end of said conductive contact means to prevent withdrawal of said cables and conductor sleeve from said body in a longitudinal direction opposite the direction of insertion.
 2. A corona free coupling structure comprising a pair of high voltage coaxial cables having outer shielding systems and a coupling assembly including a filler body of elastomeric insulating material having an elongated bore open at opposite ends receiving the end portions of said pair of cables; tubular, conductive inner shield means embedded in said body in coaxial alignment in said bore and spaced from said opposite ends thereof; a tubular connector sleeve inserted into said bore and said inner shield means connecting the central conductors of said cables in end-to-end relation; conductive contact means mounted on said conductor sleeve including a deflectable free and portion biased outwardly thereof making electrical contact between said sleeve and said inner shield means; and conductive outer shield means around said insulating body connecting the outer shielding systems of said cables; said conductive contact means includes a pivot leg extending transversely through said connector sleeve adjacent the central portion thereof for supporting the inner end of said free end portion for pivotal movement.
 3. The coupling structure of claim 2 wherein said free end portion is pivotal between oppositely extending positions on a plane longitudinally of said connector sleeve.
 4. The coupling structure of claim 3 wherein said free end portion is normally biased to extend angularly outwardly of said sleeve while on said longitudinal plane. 